Devices and methods for converting alternating current (AC) power to direct current (DC) power

ABSTRACT

Methods, circuit designs, systems, and devices for the conversion of high voltage alternating current (AC) to low voltage, high current direct current (DC) are described. An exemplary apparatus includes a rectifier for receiving a high voltage AC line power input and for outputting a full wave, high voltage DC, a gating component coupled to the rectifier for receiving the high voltage DC output by the rectifier, wherein the gating component is configured to gate the high voltage DC by turning on at a zero crossing level and turning off when the high voltage DC exceeds a preset voltage threshold and wherein the output of the gating component is an intermediate voltage DC capped by the preset voltage threshold, and a DC-DC converter coupled to the gating component for receiving the intermediate voltage DC output by the gating component, wherein the DC-DC converter is configured to step down and smooth out the intermediate voltage DC to a desired high current, low voltage DC output.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) of U.S.Provisional Patent Application Ser. No. 60/988,565, entitled “Methodsand Devices for Converting Alternating Current (AC) Mains Power toDirect Current (DC) Power,” filed Nov. 16, 2007, which is incorporatedherein by reference as if set forth herein in its entirety.

TECHNICAL FIELD

The present invention relates generally to the conversion of highvoltage alternating current (AC) to low voltage direct current (DC), andmore particularly to devices and methods for converting high voltage ACto low voltage high current DC without the use of large high voltagefilter capacitors or large high voltage switching power supplies.

BACKGROUND

Numerous applications, such as solid-state electricity metering andelectricity grid automation devices, require accommodation of highvoltage AC as input power yet must provide low voltage/high current DCoutput power for use by analog and digital circuitry. The poweravailable in these environments, known as “line power,” is typicallysupplied by an AC electric power utility and is usually within the rangeof 80 VAC and 600 VAC. The line power is the only power available foruse with these types of applications, and the circuit board area andenclosure volume available to accommodate the power supply is often verylimited.

Conventional systems attempt to provide AC to DC conversion, aspresented in detail for example in U.S. Pat. No. 6,169,391, in fourbroad categories of power supplies: the transformer approach, the highvoltage linear regulator approach, the high voltage capacitive couplingapproach, and the switching power supply approach.

The transformer-based power supplies approach uses a step downtransformer and some type of wave rectification. However, thedisadvantage to all transformer approaches is the large size, cost, andpower consumption of step down transformers, or the large size of othercomponents such as capacitors that are used in conjunction with smallertransformers.

The high voltage linear regulator approach eliminates the large, costlystep down transformer, but has the disadvantage of large capacitors andhigh power dissipation requirements.

The high voltage capacitive coupling power supplies approach alsoeliminates the step down transformer and reduces power consumption butadds design complexity and requires large capacitive elements.

The switching power supplies approach produces low voltage DC from highvoltage AC by switching at a high frequency such that transformer sizecan be reduced. However, the transformer and switch elements inswitching power supplies must be rated high enough to withstand the linevoltage and switching transients. The filter capacitors at the input toswitching power supplies must be rated to withstand the maximum linevoltage and are required to have enough capacitance to maintain thevoltage ripple within acceptable limits at the minimum line voltage.These two conditions result in physically large capacitors. These highvoltage elements greatly increase the size and cost of switching powersupplies and make it difficult to use these power supplies in spaceconstrained applications, such as solid-state electricity metering andelectricity grid automation devices.

For example, FIG. 1 is a diagram of a conventional switching powersupply used to convert the AC line voltage 110 and produce DC outputvoltage 170. The power supply includes a bridge rectifier 120 and aDC-DC converter 100. It will be understood by those skilled in the artthat the filter capacitor 130, the switch 140, and the transformer 150all must be rated to withstand the peak of the maximum input voltage 110with an adequate margin of safety. For example, for 600VAC input thispeak voltage is 848.5V. Thus, the filter capacitor 130, the switch 140,and the transformer 150 must be capable of withstanding 848.5V plus anyswitching transients that may be generated. The qualitative relationshipbetween maximum input voltage (X-axis) and the size of the switchingpower supply (Y axis) is shown in FIG. 2. Exponential growth curve 200indicates the relative effect of accommodating a large maximum inputvoltage on power supply size.

Some switching power supplies are commercially available as single chipsolutions with an external switch. For example, a company calledSupertex Inc., based in Sunnyvale, Calif. (see http://www.supertex.com)currently manufactures gating integrated circuits (ICs), such as theSR086 and SR087, which implement gating functions in a small SO-8footprint. One of Supertex's patents, U.S. Pat. No. 6,169,391, disclosesa device shown schematically herein in FIG. 3, which rectifies andregulates high voltage alternating current without the use oftransformers, large capacitive coupling circuits, or high voltage linearregulators. The device includes a rectifier 320, a control circuit 330for sensing the output voltage 350 of the rectifier 320 and switching onand off the input power, a storage capacitor 380 and a low voltagelinear regulator 340. The control circuit 330 effectively divides thedevice into a high voltage subsystem 310 and a low voltage subsystem315. Although this device allows conversion of high voltage AC to lowvoltage DC without the use of transformers, large capacitive couplingcircuits, or high voltage linear regulators, the available current atthe output 370 is less than 100 mA, which is not sufficient or suitablefor use by solid-state electricity metering and electricity gridautomation devices or any other application/components that requiresmore power or current.

Further, power supplies based on this type of design have typicallyattempted to produce logic level voltages (e.g., 3.3 V, 5.0 V) byreducing the gating-on time to a very low value. This results in veryshort duration high amplitude current spikes being drawn from the ACline, which, in turn, causes noise issues and also limits the availablecurrent to less than 100 mA, which reduces output power. Efficiency isalso reduced because at small conduction angles, the time required bythe switch to transition between the ‘on’ state and the ‘off’ state is asignificant percentage of the total ‘on’ time. This transition period isa highly dissipative state of the switch and causes losses due toheating.

FIG. 4A through FIG. 4D illustrate a voltage waveform at differentpoints in the circuit of FIG. 3. As shown in FIG. 4A, the voltagewaveform 400 of the input 350 to the control circuit 330 is a rectifiedform of the input voltage at the same magnitude as the input voltage.The typical output from control circuit 330 for such an input 350 wouldbe the voltage waveform 410 as shown in FIG. 4B, in which the circuit isclosed whenever the full wave rectified voltage is below a prescribedthreshold voltage 440, such as 40 Volts. However, the waveform 420 inFIG. 4C shows how the output 360 of the control circuit 330 is altereddue to the presence of capacitor 380 in the circuit design of FIG. 3.The low voltage linear regulator 340 of FIG. 3 then produces theregulated DC output voltage waveform 430 as shown in FIG. 4D, though ata limited output power as noted above.

There is therefore a need for improved systems, devices, and circuitdesigns for converting high voltage AC to low voltage DC without the useof large high voltage filter capacitors or large high voltage switchingpower supplies, while also providing for high current DC outputs.

There is a further need to provide methods, systems, circuit designs,and devices to reduce the size and cost of a power supply module.

There are additional needs to provide methods, systems, circuit designs,and devices to increase the input voltage range of a DC-DC converter ofa given size.

There are additional needs to provide methods, systems and designs toincrease the input voltage range of a low voltage switching power supplyof a given size.

There are further needs to provide methods, systems and designs to beable to use a low voltage (less than 80VDC input voltage range) DC-DCconverter in high voltage (80 to 600V) applications.

There are additional needs for methods, systems and designs, whereinhigh voltage AC is not allowed to propagate beyond a full wave rectifierand a transistor switch.

There are additional needs for methods, systems and designs, wherein afilter capacitor is required to be rated to only withstand a low voltageDC and not high AC line voltage.

There are yet further needs for methods, systems and designs, whereinthe output power of a power supply does not change significantly withthe output voltage.

There are additional needs for methods, systems and designs, wherein theneed for large capacitive circuits and high voltage switching powersupply is eliminated.

SUMMARY

Briefly described, and according to one embodiment, improved devices,circuit designs, systems, and methods for converting high voltagealternating current (AC) to low voltage direct current (DC) aredisclosed herein. In one embodiment, an apparatus for convertingalternating current (AC) line power to direct current (DC) power,comprises a rectifier for receiving a high voltage AC line power inputand for outputting a full wave, high voltage DC, a gating componentcoupled to the rectifier for receiving the high voltage DC, output bythe rectifier, wherein the gating component is configured to gate thehigh voltage DC by turning on at a zero crossing level and turning offwhen the high voltage DC exceeds a preset voltage threshold and whereinthe output of the gating component is an intermediate voltage DC cappedby the preset voltage threshold, and a DC-DC converter coupled to thegating component for receiving the intermediate voltage DC output by thegating component, wherein the DC-DC converter is configured to step downand smooth out the intermediate voltage DC to a desired high current,low voltage DC output.

In one feature of this embodiment, the rectifier is a bridge rectifier.

In another feature, the gating component is configured to remain offafter the high voltage DC exceeds the preset voltage threshold and untilthe next zero crossing level. In another feature, the gating componentincludes transistor switches. Preferably, such transistor switchesinclude one or more of an enhancement mode MOSFET, a depletion modeMOSFET, a bipolar transistor, a photo transistor, an IGBT (insulatedgate bipolar transistor), an ESBT (emitter-switched bipolar transistor),and an SCR (silicon controlled rectifier).

In another feature, the gating component is a dimmer switch. Preferably,the high voltage AC line power input to the rectifier is preferablywithin the range of 60 to 480 voltage AC—particularly if the gatingcomponent is a dimmer switch.

In one specific commercial application, the high voltage AC line powerinput to the rectifier is preferably within the range of 80 to 600voltage AC. However, it will be understood that the present apparatusand technology (and various components) are suitable for scaling up ordown depending upon the needs of the particular application or use andare not tied to any specific VAC input limits.

In another specific commercial application, the preset voltage thresholdis preferably set to 50 volts DC and the desired (or corresponding) highcurrent, low voltage DC output is approximately 4 volts DC at 1000milliamperes (mA).

Advantageously, with this embodiment, electronic components of the DC-DCconverter only have to be rated high enough to handle (and can be sizedmuch smaller than conventional DC-DC converter components because theyonly need to be able to handle) voltage levels up to the preset voltagethreshold of the gating component.

Preferably, the DC-DC converter includes an input capacitor forsmoothing out the intermediate voltage DC received from the gatingcomponent, a switch and a transformer for stepping down the intermediatevoltage DC, and an output capacitor for smoothing out the stepped downintermediate voltage DC from the transformer to create the desired, highcurrent, low voltage DC output. The DC-DC converter is or may be knownalternatively as a low voltage switching power supply.

In some embodiments, a second output capacitor may be coupled to theoutput of the DC-DC converter to further smooth high current, lowvoltage DC output.

It will be understood by those skilled in the art that the output of thegating component is the intermediate voltage DC capped by the presetvoltage threshold regardless of the high voltage AC line power input tothe rectifier.

In another embodiment, an apparatus for converting high voltage DC tohigh current, low power DC, comprises a gating component configured toreceive a rectified, full wave, high voltage DC, wherein the gatingcomponent is configured to gate the rectified, full wave, high voltageDC only between each zero crossing level and a preset voltage thresholdassociated with the rectified, full wave, high voltage DC and whereinthe output of the gating component is a series of intermediate voltageDC waves capped by the preset voltage threshold, and a DC-DC convertercoupled to the gating component for receiving the intermediate voltageDC waves output by the gating component, wherein the DC-DC converter isconfigured to step down and smooth out the intermediate voltage DC to adesired high current, low voltage DC output.

In a feature, the gating component includes transistor switches.Preferably, such transistor switches include one or more of anenhancement mode MOSFET, a depletion mode MOSFET, a bipolar transistor,a photo transistor, an IGBT, an ESBT, and a silicon controlled rectifier(SCR).

In another feature, the gating component is a dimmer switch. Preferably,the high voltage AC line power input to the rectifier is preferablywithin the range of 60 to 480 voltage AC—particularly if the gatingcomponent is a dimmer switch.

In one specific commercial application, the high voltage AC line powerinput to the rectifier is preferably within the range of 80 to 600voltage AC. However, it will be understood that the present apparatusand technology (and various components) are suitable for scaling up ordown depending upon the needs of the particular application or use andare not tied to any specific VAC input limits.

In another specific commercial application, the preset voltage thresholdis preferably set to 50 volts DC and the desired (or corresponding) highcurrent, low voltage DC output is approximately 4 volts DC at 1000milliamperes (mA).

Advantageously, with this embodiment, electronic components of the DC-DCconverter only have to be rated high enough to handle (and can be sizedmuch smaller than conventional DC-DC converter components because theyonly need to be able to handle) voltage levels up to the preset voltagethreshold of the gating component.

Preferably, the DC-DC converter includes an input capacitor forsmoothing out the intermediate voltage DC received from the gatingcomponent, a switch and a transformer for stepping down the intermediatevoltage DC, and an output capacitor for smoothing out the stepped downintermediate voltage DC from the transformer to create the desired, highcurrent, low voltage DC output. The DC-DC converter is or may be knownalternatively as a low voltage switching power supply.

In some embodiments, a second output capacitor may be coupled to theoutput of the DC-DC converter to further smooth high current, lowvoltage DC output.

It will be understood by those skilled in the art that the output of thegating component is the intermediate voltage DC capped by the presetvoltage threshold regardless of the high voltage AC line power input tothe rectifier.

In another embodiment, a method for converting alternating current (AC)line power to direct current (DC) power, includes the steps ofrectifying a high voltage AC line power input and outputting a fullwave, high voltage DC, gating the full wave, high voltage DC by turningon at a zero crossing level and turning off when the high voltage DCexceeds a preset voltage threshold and, thereby, outputting a series ofintermediate voltage DC waves capped by the preset voltage threshold,stepping down the series of intermediate voltage DC waves to a lowervoltage DC, and smoothing AC ripples from the lower voltage DC to createa desired, high current, low voltage DC output.

In a feature, the step of gating further comprises remaining off afterthe full wave, high voltage DC exceeds the preset voltage threshold anduntil the next zero crossing level.

In another feature, the method further comprises the step of smoothingAC ripples in series of intermediate voltage DC waves prior to the stepof stepping down the intermediate voltage DC to the lower voltage DC.

In yet a further feature, the step of gating when the high voltage DCexceeds the preset voltage threshold protects electronic componentsresponsible for the steps of stepping down and smoothing AC ripples.

In another feature, the components responsible for the steps of steppingdown and smoothing AC ripples in the intermediate voltage only have tobe rated to withstand voltages up to the preset voltage threshold.

In a further feature, the method further comprises the step of receivingthe high voltage AC line power input.

In a further feature, the method further comprises the step of providingthe desired, high current, low voltage DC output to other electroniccomponents.

Other systems, circuit designs, devices, apparatuses, methods,processes, features, commercial applications, uses, and advantages ofthe present invention and scaled up or scaled down variations of thesame will be or become apparent to one with skill in the art uponexamination of the following drawings and detailed description. It isintended that all such additional systems, methods, features andadvantages be included within this description and be within the scopeof the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the invention can be better understood with reference tothe following drawings. The components in the drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the present invention. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views.

FIG. 1 is a schematic of a conventional low voltage switching powersupply.

FIG. 2 is a plot of the qualitative relationship between the size of alow voltage switching power supply and the required maximum inputvoltage of the conventional low voltage switching power supply of FIG.1.

FIG. 3 is a schematic illustrating a conventional power supply using acontrol circuit to divide high voltage and low voltage subsystems.

FIGS. 4A-4D illustrate the voltage waveforms corresponding to variouslocations on the schematic of the conventional power supply of FIG. 3.

FIG. 5 is a schematic of a preferred power supply module disclosed anddescribed herein.

FIGS. 6A and 6B illustrate alternative and exemplary methods and systemsfor implementing the gating component or gating function of thepreferred power supply module shown in FIG. 5.

FIGS. 7A-7H illustrate the voltage waveforms corresponding to variouslocations on the schematic of the preferred power supply module of FIG.5.

FIG. 8 is a flow chart illustrating the high level steps taken to reducehigh voltage AC to low voltage high current DC using a module similar tothat shown in FIG. 5.

FIGS. 9A and 9B show a detailed circuit diagram of one embodiment ofcomponents of the supply module disclosed and described in connectionwith FIG. 5.

FIGS. 10A and 10B are drawings showing the difference in size between aconventional low voltage switching power supply for high voltage input(FIG. 10A) and a preferred embodiment of an improved apparatus disclosedand described herein (FIG. 10B), given identical input and outputconstraints.

FIG. 11 is a plot of the qualitative relationship between the size of alow voltage switching power supply and the required maximum inputvoltage, and the qualitative relationship between a low voltageswitching power supply for high voltage input and one preferredembodiment of an improved apparatus disclosed and described herein,given identical input and output constraints.

DETAILED DESCRIPTION

Reference is now made in detail to the description of the preferred andexemplary embodiments of devices, systems, and methods for convertinghigh voltage alternating current (AC) to low voltage direct current(DC), as illustrated in the accompanying drawings. The devices, systems,and methods disclosed herein may, however, be embodied in many differentforms and should not be construed as limited to the embodiments setforth herein; rather, these embodiments are intended to convey the scopeof the inventions to those skilled in the art. Furthermore, all“examples” given herein are intended to be non-limiting.

Various embodiments are described with reference to the drawings,wherein like reference numerals are used to refer to like elementsthroughout. In the following description, for purposes of explanation,numerous specific details are set forth in order to provide a thoroughunderstanding of one or more embodiments. It may be evident, however,that such embodiments may be practiced without these specific details.In other instances, well-known structures and devices are shown in blockdiagram form in order to facilitate describing one or more embodiments.

Turning now to FIGS. 5 and 7, FIG. 5 is a schematic illustrating apreferred embodiment of a power supply module 500 for converting highvoltage alternating current (AC) to low voltage direct current (DC)without the need for large filtering capacitors or high voltageswitching power supplies. FIG. 7A through FIG. 7D and FIG. 7E throughFIG. 7H illustrate a voltage waveform at different points in thecircuit/power supply module of FIG. 5, as will be described in greaterdetail herein. As will become apparent to one of skill in the art, sucha system and design provides a substantial increase in output power atlower output voltages with smaller individual components and smalleroverall system size.

Specifically, turning to FIG. 5, a bridge rectifier 520 rectifies the ACinput, which may range from 80 to 600VAC, and provides a full waverectified DC waveform at input 540 to the gating component 530, as shownby waveform 700 in FIG. 7A. The gating component 530 in effect dividesthe power supply module 500 into a high voltage subsystem 510 and a lowvoltage subsystem 515. Details of exemplary components of the highvoltage subsystem 510 and the low voltage subsystem 515 are described inconnection with FIG. 9A and FIG. 9B, respectively. A comparison of theFIG. 5 schematic with the FIG. 1 schematic shows that the capacitor 522,switch 524, and transformer 526 components in the low voltage subsystem515 are connected in the same way as the components 130, 140, and 150,respectively, of the DC-DC converter 100. In FIG. 5, the addition of thegating component 530 moves the DC-DC converter components from alocation of high voltage next to the rectifier 520 (as is done in theconventional system shown in FIG. 1) to a location of low voltage withinthe power supply—in other words, fully within the low voltage subsystem515. By reducing the voltage presented to the DC-DC converter within thelow voltage subsystem 515, the gating component 530 enables the DC-DCconverter components in the low voltage subsystem 515 to be smaller thanthey are required to be if they were included in the high voltagesubsystem 510, in which they would be required to accommodate the linevoltage directly. Another way to view the impact of the gating component530 on this system design is to consider the gating component 530 to bea way of increasing the voltage range capability of a DC-DC converter ofa given size.

In one embodiment, the gating component 530 turns on at zero crossingand turns off when the input voltage exceeds a preset voltage thresholdV_(T) (shown as threshold 780 in FIG. 7A through 7H). The switch insidegating component 530 remains off until the next zero crossing when itturns on again and the cycle is repeated. An exemplary output waveform710 of the output 550 from gating function (if there were no capacitor522 included in low voltage subsystem 515) is shown in FIG. 7B.Exemplary transistor switches to carry out the gating component 530include an enhancement mode MOSFET, a depletion mode MOSFET, a bipolartransistor, a photo transistor, an IGBT, an ESBT, and a siliconcontrolled rectifier (SCR), among other types of switch technology knownto those of skill in the art.

As one with skill in the art will appreciate from a closer study of FIG.5, in order to use a standard “off the shelf” DC-DC converter withmaximum input voltage capability of a particular voltage (e.g., 72V),one must set the gating circuit to “cut off” at that voltage (e.g.,72V). One skilled in the art will further appreciate that the inputvoltage range of any DC-DC converter can be substantially increased byusing this method. In addition, this technique also allows the DC-DCconverter to utilize AC power.

During its ON state, the gating component 530 provides low voltage DC710 as shown in FIG. 7B and the AC ripple 720 is filtered by thecapacitor 522 coupled to its output 550, as shown in FIG. 7C. When thefull wave rectified output 540 rises above the predetermined thresholdvoltage (at whatever level that is set to), the gating component 530opens (off-state, off-period) and no current flows to the low voltagesubsystem 515. Because the gating component 530 turns off and removesthe charging current to the low voltage subsystem 515 when the full waverectified output 540 increases above the predetermined thresholdvoltage, the capacitor 522 and other power supply components within thelow voltage subsystem 515 are never utilized beyond their predeterminedthreshold voltage. Since voltage for these components is limited, thelarge (and bulky) high voltage capacitors that require large portions ofprinted circuit board (PCB) space are not required in implementationsaccording to the preferred embodiments of the present systems, devices,and methods.

Within the low voltage subsystem 515, the capacitor 522 reduces the ACripples from the intermediate voltage DC at output 550 and provides apre-regulated intermediate voltage DC to the switch 524 and transformer526. These components step the pre-regulated intermediate voltage DCdown, with another capacitor 528 to further reduce the AC ripples, to apredetermined final voltage DC 560 as shown as curve 730 in FIG. 7D.

While the intermediate voltage DC 550 can optionally be adjusted bychanging the threshold voltage at which the gating function opens (turnsoff) to a different predetermined threshold voltage, such an adjustmentis no longer required for providing a low output voltage DC 560 as longas the regulated intermediate voltage DC 550 is within the input voltagerange of the low voltage subsystem 515. As a result, the output poweravailable for a particular output voltage 560 of the low voltagesubsystem 515 does not change significantly for different values ofoutput voltage 560.

It should also be noted that the conduction angle for transistors withinthe gating component 530 remains at the maximum value determined by theinput voltage rating of the low voltage subsystem 515. The largerconductions angle reduces the effect of turn-on and turn-off times ofthe gating component 530 and allows transistors within gating component530 to operate more efficiently.

Additionally, the intermediate regulated low voltage DC 550 ismaintained at the predetermined threshold voltage (50 V in thisinstance). Maintaining a value for the intermediate regulated lowvoltage DC 550 that is much higher than the voltage drop across thetransistor reduces the effect of the voltage drop across the gatingcomponent 530, and therefore is believed to improve efficiency.

The components within the low voltage subsystem 515 need only be ratedto sustain the predetermined threshold voltage of the gating circuit530. There is no need for rating these components according to the linepower 110 supplied by the AC power utility, since the high voltages donot propagate beyond the full wave rectifier 520. For example, if thepredetermined threshold voltage is 50.0 V, the components of the lowvoltage subsystem 515 need only be rated for 60.0 V rather than the 850V that would be required by a conventional switching power supplymodule. As a result, the low voltage subsystem 515 is much smaller andmore cost effective than a conventional switching power supply.

One skilled in the art will note that the high voltage subsystem 510 ofFIG. 5 is similar to the high voltage subsystem 310 of FIG. 3 in whichthe control circuit 330 performs a similar function as gating component530. However, in the conventional system design represented by FIG. 3,the low voltage subsystem 320 contains a linear regulator 340 thatconstrains the power available at output 370. In contrast the lowvoltage subsystem 515 of preferred embodiments of the present systemprovide high power at output 560.

EXAMPLE

It is apparent that the exemplary power supply module 500 describedherein provides an increase in efficiency while also providing asignificant increase in output power at low output voltages 560. In oneexemplary use, allowing for 90% efficiency for the low voltage subsystem515 and with the intent to provide an output voltage 560 of 5.0 V, theoutput power provided is given by:P=V*I*η  (1)where the V is the intermediate regulated low voltage DC 550 supplied bythe gating component 530 (50.0 V in this instance) and I is the currentat the output of the gating component 530. The efficiency of the lowvoltage subsystem 515 is represented by η. Using the above values gives:P=50.0 V*0.1A*0.90=4.5W   (2)This output power is independent of output voltage 560 because as outputvoltage 560 is reduced, the output current increases in the sameproportion.

In contrast, conventional gated power supplies working alone provide thepower according to the following standard equation:P _(conv)=V_(conv)*I_(conv)   (3)where V_(conv) is the output voltage and I_(conv) is the output current.The max output current of 0.1A stays the same at 5V or 50V and henceproviding the same output voltage 560 of 5V gives an available powerP_(conv) of:P _(conv)=0.5 V*0.1A=0.5W   (4)

As is evident in the results given in equations (2) and (4) above, theexemplary power supply module 500 provides an output power of 4.5Wcompared to 0.5W for a conventional gated power supply, or nine timesthe output power provided at 5V using a conventional gated power supply,such as the power supply 100 shown in FIG. 1. The increase in power atlower output voltages such as, for example, 3.3V and 2.5V, is even moredramatic.

FIG. 6A is a schematic illustrating another embodiment of a power supplymodule for converting high voltage alternating current (AC) to lowvoltage direct current (DC). In this embodiment, the gating component530 is carried out in the high voltage subsystem 610 a by the use of astandard dimmer switch with a simple feedback control system 630 a. Suchan embodiment is suitable, for example, when the line voltage isexpected to be between 60 and 480 VAC.

FIG. 6B is a schematic illustrating another embodiment of a power supplymodule for converting high voltage alternating current (AC) to lowvoltage direct current (DC). In this embodiment, the gating component530 is carried out in the high voltage subsystem 610 b by the use of onecomponent circuit 310 from the circuit of FIG. 3, but without using thelinear regulator 315 of the circuit in FIG. 3. Specifically, the linearregulator 310 of FIG. 3 is replaced by the DC-DC converter 515. Such anembodiment is suitable, for example, when the line voltage is expectedto be between 80 and 600 VAC.

As previously discussed, FIG. 7A illustrates a full wave rectifiedvoltage 700 according to the rectifier output voltage 540 of FIG. 5.FIG. 7B illustrates an output voltage waveform 710 corresponding to theoutput of gating component 530, if there is no capacitor 522. When thefull wave rectified output 700 voltage increases above the predeterminedthreshold voltage 780, the gating component 530 opens (turns off). Aslong as the input voltage (corresponding to the full wave rectifiedoutput shown in FIG. 7A) remains above the predetermined thresholdvoltage 780, the gating component 530 does not conduct (i.e., remainsturned off). The gating function switches to on (and thus conducts) whenthe zero crossing is reached. In preferred embodiments, thepredetermined threshold voltage 780 will be set to 50.0 V in order toachieve an output of 4 volts DC at 1 amp. However, it will be noted bythose of skill in the art that the gating component 530 may beconfigured for any desired predetermined threshold voltage according tothe input requirements of the low voltage subsystem 515. It should benoted also that, for maximization of output power and efficiency, thegating component 530 uses a transistor switch, which should typically beconfigured to have the highest threshold voltage that falls within theinput voltage range of the low voltage subsystem 515. The output voltagewaveform 710 depicts the voltage for which the gating component 530remains conducting (turned on). The capacitor 522 receives the voltagedepicted by the output voltage waveform 710 and is charged by thecorresponding current, providing a smoothed voltage waveform 720, asshown in FIG. 7C. The AC ripple at the intermediate voltage DC output550 of the gating circuit 530 is smoothed by the capacitor 522, and isprovided as the input to the remainder of the low voltage subsystem 515components 524, 526, and 528, which produce smooth DC voltage 560, asshown by voltage 730 in FIG. 7D. FIGS. 7A through FIG. 7D show thebehavior of power supply 500 when the input voltage 700 is relativelylow compared to the gating function threshold voltage 780.

By way of comparison, FIGS. 7E through FIG. 7H show the impact of a muchhigher input voltage 740 given the same gating function thresholdvoltage 780. Although the input voltages are significantly different inmagnitude, the quality of the output voltage 770 is the same and exactlythe same system components are used.

In the exemplary embodiments in FIG. 5, FIG. 6A, and FIG. 6B, theintermediate voltage DC has a rating of 50.0 V at 100 mA and the outputvoltage 560 is about 4.0 V DC with a current rating of about 1000 mA.Those of skill in the art will readily appreciate that the DC gatedpower supply may be configured to provide different values ofintermediate voltage DC to the low voltage subsystem 515. It will alsobe appreciated that the low voltage subsystem 515 may be configured toprovide different output voltage 560 values and current ratings.

The gating component 530 operates to mask changes in the input voltage,thus preventing input voltage changes from affecting the remainder ofthe circuit components in the low voltage sub system 515. The result isa wide input voltage 540 operating range that does not appreciablyaffect output voltage 560. The output voltage 560 remains unchanged eventhough the input voltage 540 changes.

The gating component 530 within the DC gated power supply operates toprevent downstream components from exposure to large DC voltages. Oncethe predetermined threshold voltage is reached, the gating circuit isturned off and the downstream exposure is limited to the value of thepredetermined threshold voltage. The large DC voltages are notpropagated beyond the full wave rectifier 520 and the gating component530.

The filter capacitors 522 and 528 are in the low voltage subsystem 515of the power supply module 500, and therefore smaller low voltagecapacitors are utilized. Also, PCB traces are closer together due tolower voltages and require less PCB space, thus further reducing thesize of the power supply module 500.

It should also be noted that since the low voltage subsystem 515 is notexposed to high voltages, its components are smaller and the designlayout is more compact, thus reducing the size of the power supplymodule 500 even further. Additionally, the variations in the inputvoltage are limited to the gating component 530 and do not reach thecomponents of the low voltage subsystem 515, allowing for a simplifieddesign. Thus, the size of the power supply module 500 is reduced evenfurther.

Another benefit of gating the full wave rectified DC on at zero crossingis reduction in noise when compared with power supplies that gate on atpeak voltage and utilize a full wave diode rectifier immediatelyfollowed by a capacitor filter.

FIG. 8 illustrates steps 800 for converting high voltage AC to lowvoltage DC according to the present methods, systems, and devices. Linepower is received from an AC power utility and the high voltage AC isrectified to a high voltage DC at step 810. The rectifying is typicallyperformed by a bridge rectifier. At step 820 a determination is madewhether the full wave rectified output, V_(Rectified), is below apredetermined threshold voltage, V_(Threshold). In one exemplaryembodiment, V_(Threshold) is 50.0 V. If V_(Rectified) is belowV_(Threshold), then a transistor switch is closed, e.g., on-state,on-period, etc, at step 830. If V_(Threshold) is not belowV_(Rectified), then the transistor switch is opened (e.g., off-state,off-period, etc.) at step 840. Typical embodiments of transistorswitches include an enhancement mode MOSFET, a depletion mode MOSFET, abipolar transistor, an IGBT, an ESBT, or a silicon controlled rectifier(SCR), among other types of switch technology.

A closed transistor switch is maintained in an on-period so long as therectified high voltage DC is below the predetermined threshold voltageV_(Threshold). AC ripples are smoothed from the low voltage DC at step850. The smoothing provides a pre-regulated low voltage DC and istypically performed by a small, low voltage capacitor. Since thetransistor switch is opened upon V_(Rectified) exceeding V_(Threshold),the voltage at the capacitor will never exceed V_(Threshold), and asmall, low voltage capacitor is all that is necessary. Since thecapacitor is never charged above V_(Threshold), the required PCB spaceis reduced.

At step 860, the smoothed pre-regulated intermediate voltage DC isprovided to a DC-DC converter. The DC-DC converter or low voltagesubsystem of an exemplary power supply module is typically a low voltageswitching power supply configured for stepping the pre-regulatedintermediate voltage DC to a predetermined low voltage DC as at step870. Typical values for the low voltage DC are 3.3 V and 5.0 V, as thesevoltages are common for usage in logic circuits and microprocessors. Ofcourse, those of skill in the art will readily appreciate that othervalues for low voltage DC may be used.

As noted above, when V_(Rectified) reaches V_(Threshold), the transistorswitch is opened, e.g., off-state, off-period, etc. at step 830. Ineither event, the pre-regulated intermediate voltage DC is maintaineduntil V_(Rectified) drops below V_(Threshold). Once V_(Rectified) dropsbelow V_(Threshold), the transistor switch is closed again.

FIG. 9A is a schematic diagram of a circuit 900 illustrating a rectifierand DC gated power supply portion of one embodiment of a power supplymodule for converting high voltage AC to low voltage DC. Circuit 900 isan embodiment of the high voltage subsystem 510 shown in FIG. 5. Linepower is typically provided from an AC power utility at header 902 andthe power supply is protected by an SMT Fuse 904 rated at 1.25 A andtransient voltage suppressors (TVS) 906 rated for 260 V and 1500 W. Ahigh voltage bridge rectifier 908 provides a full wave rectified DCvoltage to an SR086 integrated circuit (IC) 928 for gating. An outputV_(out) of 50.0V is provided from the SR086 IC 928 for input to theDC-DC converter portion in FIG. 9B.

Biasing resistors 910 and 912 for V_(In) have values of 100K ohms and261K ohms respectively. The IGBT transistor 914 provides the switchedconnection between the output of the bridge rectifier and the input tothe DC-DC converter. Resistor 916 is used in conjunction with capacitors918 to reduce EMI, capacitor 920 reduces ripple across the gate drivecircuitry, and capacitor 930 reduces ripple across the comparatorcircuitry. Capacitors 922 and 924 filter the ripple from theintermediate voltage used to feed the DC-DC converter. Resistor 926 isthe pulldown resistor for the active low enable input, and resistors 940and 942 are used to set the voltage threshold. The largest capacitor (byphysical size and capacitance) is capacitor 924.

The components of FIG. 9A provide a full wave rectified DC that is gatedon at zero crossing by the gating circuit and remains on until apredetermined threshold voltage is reached. Thus, an intermediatevoltage DC is provided that is smoothed and then provided to theswitching power supply 950 of FIG. 9B.

While typical conventional switching power supplies often requireseveral large (and bulky) high voltage capacitors, it will beappreciated that the embodiment shown in FIG. 9A and FIG. 9B includes asingle large electrolytic capacitor 924 (470 μF). The reduction in PCBsize is appreciable.

FIG. 9B is a schematic diagram illustrating a DC-DC converter 950portion of one embodiment of a power supply module for converting highvoltage AC to low voltage DC. DC-DC converter 950 and its associatedcomponents are an embodiment of the low voltage subsystem 515 shown inFIG. 5. An input voltage V_(In) of 50.0 V (V_(Out) from FIG. 9A) isprovided to the DC-DC converter 950. The DC-DC converter is configuredin this embodiment to convert the intermediate voltage DC (50.0V at 100mA) to an output voltage 952 that is about 4.0 V DC with a currentrating of about 1000mA. Those of skill in the art will readilyappreciate that the DC gated power supply portion may be configured toprovide different values of intermediate voltage DC to the DC-DCconverter or low voltage switching power supply 950. It will also beappreciated that the DC-DC converter may be configured to providedifferent output voltage 952 values and current ratings.

FIG. 10 illustrates a top view and a side view of a conventional powersupply (FIG. 10A) compared with an embodiment of the present powersupply for converting high voltage AC to low voltage DC (FIG. 10B).While not illustrated to precise scale, FIG. 10 illustrates theappreciable size reduction realized from embodiments of the presentinventions.

For example, a typical conventional power supply as shown in FIG. 10Aincludes a switching transformer 1002, six bulky 350V 22 μF capacitors1004, and two large 3300 μF capacitors 1006 for filtering the output.Additionally, there are two fusible resistors 1008 and two 520 V MOVs1010 to protect against transient voltages.

As illustrated in FIG. 10B, an exemplary embodiment according to thepresent invention requires dramatically less PCB space with its maincomponents being a fuse 1020, a bridge rectifier 1022, a single largeelectrolytic capacitor 1024, and a DC-DC converter 1026, such as a lowvoltage switching power supply.

The qualitative impact of the maximum input voltage required on the sizeof the conventional power supply (FIG. 10A) and an embodiment of thepresent invention (FIG. 10B) is shown in FIG. 11 where the curve 1110represents conventional power supplies and curve 1120 represents powersupplies built using the improved methods, devices, and systems asdescribed herein.

The foregoing description of the exemplary embodiments of the inventionhas been presented only for the purposes of illustration and descriptionand is not intended to be exhaustive or to limit the invention to theprecise forms disclosed. Many modifications and variations are possiblein light of the above teaching.

The embodiments were chosen and described in order to explain theprinciples of the invention and their practical application so as toenable others skilled in the art to utilize the invention and variousembodiments and with various modifications as are suited to theparticular use contemplated. Alternative embodiments will becomeapparent to those skilled in the art which the present inventionpertains without departing from its spirit and scope. Accordingly, thescope of the present invention is defined by the appended claims ratherthan the foregoing description and the exemplary embodiments describedtherein.

What is claimed is:
 1. An apparatus for converting alternating current(AC) line power to direct current (DC) power, comprising: a rectifierfor receiving a high voltage AC line power input and for outputting afull wave rectified high voltage DC; a voltage-reducing voltageregulating component coupled to the rectifier for receiving the fullwave rectified high voltage DC and providing an intermediate voltage DCcapped by a preset voltage threshold corresponding to said intermediatevoltage DC, wherein the regulating component is operative to supply theintermediate voltage DC by gating the full wave rectified high voltageDC at said preset voltage; and a voltage-reducing switching DC-DCconverter directly coupled to the voltage-reducing regulating componentfor receiving the intermediate voltage DC provided by thevoltage-reducing regulating component, the voltage-reducing DC-DCconverter configured to step down and smooth out the intermediatevoltage DC to a desired high current, low voltage DC output, thevoltage-reducing regulating component being coupled between therectifier and the voltage-reducing DC-DC converter to isolate the fullwave rectified high voltage DC from the voltage-reducing DC-DCconverter; and wherein the voltage-reducing regulating componentcomprises a gating component configured to gate the high voltage DC byturning on at a zero crossing level and turning off when the highvoltage DC exceeds the preset voltage threshold and remain off after thehigh voltage DC exceeds the preset voltage threshold and until the nextzero crossing level.
 2. The apparatus of claim 1, wherein the rectifieris a bridge rectifier.
 3. The apparatus of claim 1, wherein thevoltage-reducing regulating component includes transistor switches. 4.The apparatus of claim 3, wherein the transistor switches comprise oneor more of an enhancement mode MOSFET, a depletion mode MOSFET, abipolar transistor, a photo transistor, an IGBT, an ESBT, and a siliconcontrolled rectifier (SCR).
 5. The apparatus of claim 1 , wherein thehigh voltage AC line power input to the rectifier is within the range of60 to 480 voltage AC.
 6. The apparatus of claim 1, wherein the highvoltage AC line power input to the rectifier is within the range of 80to 600 voltage AC.
 7. The apparatus of claim 1, wherein the presetvoltage threshold is 50 volts DC and the desired high current, lowvoltage DC output is approximately 4 volts DC at 1000 milliamperes (mA).8. The apparatus of claim 1, wherein components of the voltage reducingDC-DC converter only have to be rated high enough to handle voltagelevels up to the preset voltage threshold of the voltage-reducingregulating component.
 9. The apparatus of claim 1, wherein thevoltage-reducing DC-DC converter includes an input capacitor forsmoothing out the intermediate voltage DC received from thevoltage-reducing regulating component, a switch and a transformer forstepping down the intermediate voltage DC, and an output capacitor forsmoothing out the stepped down intermediate voltage DC from thetransformer to create the desired, high current, low voltage DC output.10. The apparatus of claim 1, wherein a second output capacitor iscoupled to the output of the voltage-reducing DC-DC converter to furthersmooth high current, low voltage DC output.
 11. The apparatus of claim1, wherein the intermediate voltage DC is 50 volts DC.
 12. The apparatusof claim 1, wherein the rectifier provides a high side and a low sidefor the full wave rectified high voltage DC, and wherein thevoltage-reducing voltage regulating component is coupled between therectifier and the DC-DC converter on the high side.
 13. An apparatus forconverting an input high voltage DC to high current, low voltage DC,comprising: a voltage-reducing voltage regulating component operative toreceive the input high voltage DC and provide an intermediate voltage DCcapped by a preset voltage threshold corresponding to said intermediatevoltage DC, wherein the voltage-reducing regulating component isoperative to supply the intermediate voltage DC by gating the input highvoltage DC at said preset voltage threshold; and a voltage-reducingswitching DC-DC converter coupled to the voltage-reducing regulatingcomponent for receiving the intermediate voltage DC output provided bythe voltage-reducing regulating component, the voltage-reducing DC-DCconverter configured to step down and smooth out the intermediatevoltage DC to a desired high current, low voltage DC output, thevoltage-reducing regulating component being coupled directly to thevoltage reducing DC-DC converter to isolate the input high voltage DCfrom the voltage reducing DC-DC converter; and wherein thevoltage-reducing regulating component comprises a gating componentconfigured to gate the high voltage DC by turning on at a zero crossinglevel and turning off when the high voltage DC exceeds the presetvoltage threshold and remain off after the high voltage DC exceeds thepreset voltage threshold and until the next zero crossing level.
 14. Theapparatus of claim 13, wherein the voltage-reducing regulating componentincludes transistor switches on the high side of the input high voltageDC.
 15. The apparatus of claim 14, wherein the transistor switchescomprise one or more of an enhancement mode MOSFET, a depletion modeMOSFET, a bipolar transistor, a photo transistor, an IGBT, an ESBT, anda silicon controlled rectifier (SCR).
 16. The apparatus of claim 13,wherein the preset voltage threshold is 50 volts DC and the desired highcurrent, low voltage DC output is approximately 4 volts DC at 1000milliamperes (mA).
 17. The apparatus of claim 13, wherein thevoltage-reducing DC-DC converter includes an input capacitor forsmoothing out the intermediate voltage DC received from thevoltage-reducing regulating component, a switch and a transformer forstepping down the intermediate voltage DC, and an output capacitor forsmoothing out the stepped down intermediate voltage DC from thetransformer to create the desired, high current, low voltage DC output.18. The apparatus of claim 13, wherein a second output capacitor iscoupled to the output of the voltage-reducing DC-DC converter to furthersmooth high current, low voltage DC output.
 19. The apparatus of claim13, wherein components of the voltage reducing DC-DC converter only haveto be rated high enough to handle voltage levels up to the presetvoltage threshold of the voltage-reducing regulating component.
 20. Theapparatus of claim 13, wherein the high voltage DC is a full waverectified high voltage DC.
 21. The apparatus of claim 13, wherein theintermediate voltage DC is 50 volts DC.
 22. The apparatus of claim 13,wherein the input high voltage DC comprises a high side and a low side,and wherein the voltage-reducing voltage regulating component is coupledbetween the input high voltage DC and the DC-DC converter on the highside.
 23. A method for converting alternating current (AC) line power tolow voltage direct current (DC) power, comprising the steps of:rectifying a high voltage AC line power input to provide a full waverectified high voltage DC; coupling the full wave rectified high voltageDC directly to an isolating intermediate voltage regulator; continuouslyregulating the full wave rectified high voltage DC with the isolatingintermediate voltage regulator to provide a regulated intermediatevoltage DC capped at a preset voltage threshold; directly coupling theregulated intermediate voltage DC to a voltage-reducing low voltageDC-DC switching power supply; and providing a desired, high current, lowvoltage DC output from the voltage-reducing low voltage DC-DC switchingpower supply; gating the full wave rectified high voltage DC by turningon a switch at a zero crossing level and turning off the switch when thehigh voltage DC exceeds the preset voltage threshold and, therebyoutputting a series of intermediate voltage DC waves capped by thepreset voltage threshold, and the switch remaining off after the fullwave, high voltage DC exceeds the preset voltage threshold and until thenext zero crossing level whereby the isolating intermediate voltageregulator isolates the high voltage AC line power from thevoltage-reducing low voltage switching power supply with a regulatedintermediate voltage DC.
 24. The method of claim 23, wherein the fullwave rectified high voltage DC comprises a high side and a low side, andwherein the step of continuously regulating the full wave rectified highvoltage DC is effected by the isolating voltage-reducing voltageregulating component coupled between the high side of the wave rectifiedhigh voltage DC and the voltage-reducing low voltage switching powersupply.
 25. The method of claim 23, further comprising the step ofstepping down the series of intermediate voltage DC waves to a lowervoltage DC; and smoothing AC ripples in the series of intermediatevoltage DC waves prior to the step of stepping down the intermediatevoltage DC to the lower voltage DC.
 26. The method of claim 23, whereinthe step of providing the regulated intermediate voltage DC protectselectronic components responsible for the steps of stepping down andsmoothing AC ripples.
 27. The method of claim 26, wherein the componentsresponsible for the steps of stepping down and smoothing AC ripples onlyhave to be rated to withstand voltages up to the preset voltagethreshold.
 28. The method of claim 23, further comprising the step ofproviding the desired, high current, low voltage DC output to electroniccomponents.